In recent years, these electronic devices made of organic materials have been actively studied. These electronic devices (organic electronic devices) can be mounted on flexible and large-area substrates and can be manufactured in a low-temperature process at low cost, for example. These advantages over conventional electronic devices made of inorganic materials are expected to realize, for example, practical flexible displays etc.
Examples of the organic electronic device includes organic electroluminescent (hereinafter referred to as “organic EL”) device, organic photovoltaic cells, and organic field-effect transistors (organic FETs), etc.
The organic EL device includes an organic EL element in which an organic layer containing a luminescent material is interposed between a pair of electrodes. The organic EL element has characteristics, such as low voltage drive, high luminance, light emission capability, etc., and therefore, can have a smaller thickness and a lower weight. The organic EL device can be used in light source applications for optical communication and illumination applications in addition to display applications. For example, an organic EL illuminating device has many advantages, such as surface emission, smaller thickness, ease of dimming control, free of materials, such as mercury etc., which put a high load on the environment, etc.
Incidentally, when the organic EL device is used in illumination applications and optical communication applications, a higher emission luminance is required than in display applications. However, if a drive current is increased to enhance the luminance of the organic EL device, the organic EL element is more easily degraded, leading to a shorter lifetime of a device including the organic EL element.
For example, PATENT DOCUMENT 1 describes an organic EL illuminating device which includes an organic EL element including a large number of light emitting units having an emission area of 0.2 mm2 or less arranged in a matrix, and can emit light with high luminance and high illuminance.
PATENT DOCUMENT 2 describes an EL illuminating device including a lens sheet having a minute uneven structure (including protruding portions and recessed portions) formed in a surface thereof. The lens sheet is provided on a side of an EL element from which light is emitted, to change the direction of emitted light. As a result, the luminance in the front direction can be enhanced and the lifetime of the EL element can be increased.